This invention relates generally to a cooking device and more particularly to a pressure fryer of the type having a pressure-tight cooking vessel which is adapted to hold a bath of cooking oil and a food product such as chicken. The vessel of such a fryer may be heated either electrically or by a gas burner and is equipped with a removable cover which is adapted to be sealed to the vessel to establish a pressure-tight condition therein.
The fryer is operated by placing a quantity of cooking oil in the vessel, by activating the heater to raise the temperature of the oil, by placing the food product in the vessel and by then sealing the vessel with the cover. Pressure is generated in the vessel as the moisture in the product reaches the boiling point and vaporizes into steam. The pressure which is generated reduces the cooking time and also raises the boiling point of the juices in the product so that flavor is sealed in and less shrinkage occurs.
To prevent the operator of the fryer from being burned by hot oil, it is essential that the cover of the vessel be locked in its closed and sealed position as long as there is any substantial pressure in the vessel. If the cover should happen to be unsealed and opened while the vessel is pressurized, hot oil would explode from the vessel and could seriously burn the person who is operating the fryer.
Various arrangements have been devised in order to keep the cover locked in a closed position while the vessel is pressurized. One such arrangement involves the use of a pressure-responsive plunger which is slidably mounted in the cover. As pressure builds up in the vessel, it forces the plunger to a locking position in which the plunger engages the opening-closing actuator of the cover and prevents the actuator from being operated in a direction to open the cover. When the pressure is relieved, the plunger releases the opening-closing actuator of the cover to permit opening of the cover.
Since the locking plunger is exposed to the pressure in the vessel, it requires frequent cleaning and servicing to prevent cooking oil and food product from interfering with the sliding motion of the plunger. Also, the plunger sometimes may act erractically and permit the cover to be opened before the pressure in the vessel has been reduced to a definitely safe value.